1. Field of the Invention
The present invention relates to septic tank systems and, more particularly, to ultraviolet light disinfection units for septic tank systems.
2. Description of the Related Art
Many people living in rural areas are not served by municipal sewage systems and must utilize a septic tank system or other method to treat their domestic wastewater. A conventional septic tank system includes two primary components, a septic tank and a drainfield. The septic tank receives the raw sewage. In the septic tank, the heavy solids settle to the bottom of the tank where the organic solids are decomposed by anaerobic digestion. Lighter solids float to the top of the liquid layer in the septic tank and form a layer of scum. The liquid effluent, with the solids removed therefrom, is then discharged from the septic tank. Septic tanks can have a simple single compartment design or may include multiple compartments, baffles and other structures designed to remove a larger percentage of the solids from the wastewater before the liquid effluent is discharged from the septic tank. A pump may be utilized to discharge the liquid effluent from the septic tank, or, in a gravity flow system, liquid effluent is discharged from the tank as additional sewage enters the tank.
After the liquid effluent is discharged from the septic tank, a downstream fluid system conveys the effluent to a location where it is discharged into the environment. Typically, the effluent is discharged into a drainfield or from a surface discharge pipe. The use of a drainfield is more common and a typical drainfield includes a distribution box that receives the effluent and then distributes it to several perforated pipes. The perforated pipes are located below grade in a gravel-filled trench. The effluent is discharged from the perforated pipes into the gravel-filled trench where it percolates into the surrounding soil. As the effluent percolates through the surrounding soil the effluent is filtered by the soil and undergoes treatment by chemical and biological processes that occur within the soil layer before the effluent reaches an underlying water table or a body of surface water.
Recently, it has become more common to treat the effluent within the septic tank system with ultraviolet light before it is discharged into the surrounding environment either through a drainfield or surface discharge pipe. Exposure to ultraviolet light kills many of the microorganisms present in the liquid effluent discharged from the septic tank system and many of the governmental bodies responsible for regulating the installation and operation of septic tanks are mandating performance levels that require a secondary treatment, e.g., exposure to ultraviolet light, of the liquid effluent before it is released to the environment.
Although septic tank systems which utilize ultraviolet light treatment of the liquid effluent discharged from the septic tank are known, the improvement of such systems is desirable.